An air conditioner for vehicles is an apparatus embedded in a car in order to cool or heat the inside of a car in summer or winter or secure a front and back view of a driver by defrosting a windshield, or the like, in rainy weather or in winter. Generally, the air conditioner has both a heating system and a cooling system to selectively intake outside air or inside air, heat or cool the air, and blow the heated or cooled air to the inside of a car, thereby cooling, heating, or ventilating the air.
As shown in FIG. 1, a general refrigerant cycle of the air conditioner is generally made by a refrigerant pipe 5, wherein the refrigerant pipe 5 connects a compressor 1 compressing and delivering a refrigerant, a condenser 2 condensing the high-pressure refrigerant delivered from the compressor 1, an expander 3 throttling the refrigerant condensed and liquefied in the condenser 2, an evaporator 4 evaporating the low-pressure liquid refrigerant throttled in the expander 3 by heat-exchanging it with air blown to the inside of a car to cool air discharged to the inside of a car by an endothermic action due to evaporation latent heat, or the like, thereby cooling the inside of a car through the following refrigerant circulation process.
The refrigerant cycle according to the prior art will be described in detail.
If a cooling switch (not shown) of an air conditioner for vehicles is turned-on, a compressor 1 is first driven by the power of an engine to intake air and compresses a low-temperature and a low-pressure gas refrigerant in order to convert it into a high-temperature and a high-pressure gas and delivers it to a condenser 2 and the condenser 2 condenses a gas refrigerant into a high-temperature and high-pressure liquid by heat-exchanging the gas refrigerant with outside air.
Next, the liquid refrigerant delivered in the high-temperature and high-pressure state from the condenser 2 is rapidly expanded by the throttling action of the expander 3 and is then delivered to the evaporator 4 in a low-temperature and low-pressure wet state and the evaporator 4 heat-exchanges the refrigerant while the air is blowing into the inside of a car by a blower (not shown).
In addition, the refrigerant introduced into the evaporator 4 is evaporated during the circulating process of the evaporator 4 and discharged in the low-temperature and low-pressure gas state and again sucked into the compressor 1, thereby re-circulating the above-mentioned refrigerant cycle.
In the above-mentioned refrigerant circulating process, cooling the inside of a car is done by blowing cool air by the blower (not shown) with the evaporation latent heat of the liquid refrigerant circulating inside of the evaporator 4 while passing through the evaporator 4 and discharging the cooled air to the inside of a car.
In this case, a receiver driver (not shown) separating the liquid refrigerant is installed between the condenser 2 and an expansion valve 3, thereby making it possible to supply only the liquid refrigerant to the expansion value 3.
However, since the above-mentioned refrigerant cycle has a limitation in increasing cooling performance, improvement for increasing the cooling performance is urgently required. Further, there is a limitation in increasing the efficiency of the entire system due to the loads of the compressor 1.
In particular, in order to increase the cooling efficiency of the entire system, a need exists for a method for decreasing the pressure drop amount of the refrigerant and increasing the refrigerant flow to increase evaporation conditionality while shortening a passage length of the refrigerant by complexly considering the flow length and pressure drop amount of the refrigerant, the refrigerant flow, or the like, in particular, when the refrigerant flow velocity is the same.
An example of the expansion valve 3 is shown in FIG. 2.
FIG. 2 shows a thermal expansion valve (TXV), which reduces the high-temperature and high-pressure liquid refrigerant to the low-temperature and low-pressure liquid refrigerant, controls the refrigerant flow, and the entire pressure balance of the refrigerant cycle.
Referring to FIG. 2, the TXV is configured to include a main body 31 having an orifice 34 formed at the lower portion thereof between an inflow passage 32 and a discharge passage 33 in order to expand the refrigerant supplied from the condenser 2 and then supply it to the evaporator 4 and a connection passage 37 formed at the upper portion thereof in order to supply the refrigerant discharged from the evaporator 4 to the compressor 1, a valve 35 controlling the refrigerant flow passing through the orifice 34, and a shaft 38 moving the valve 35 while being elevated by a diaphragm 36 displaced according to the change in temperature of the refrigerant moving in the connection passage 37.
However, since the air conditioner to which the above-mentioned refrigerant cycle is applied uses the evaporator including the single evaporator unit, it has a limitation in improving the radiating performance and the cooling efficiency (COP).